1. Technical Field
The present disclosure relates to a common voltage generation circuit and a liquid crystal display circuit comprising the same.
2. Discussion of Related Art
A liquid crystal display (LCD) is a type of flat panel display for displaying images using liquid crystals. In general, LCDs feature low power consumption, slim, lightweight design, with low driving voltage.
A conventional LCD includes a color fitter display panel having reference electrodes and color filters, a thin film transistor (TFT) substrate having TFTs and pixel electrodes, and a liquid crystal layer sandwiched between the color filter display substrate and the TFT substrate. An LCD displays images by applying electric potentials to the pixel electrodes and the reference electrodes to generate an electric field in the liquid crystal layer to control the alignment of the liquid crystal molecules and the quantity of light transmitted is controlled.
In conventional LCDs, in order to reduce or prevent deterioration of a liquid crystal layer, polarity inversion of a liquid crystal voltage is periodically performed within each frame, which is called a frame inversion driving method. The liquid crystal voltage is determined by a data voltage applied to a data driver and a common voltage corresponding to the data voltage.
In recent years, several attempts have been made to improve the display quality of LCD devices. In polarity inversion, a positive-polarity voltage and a negative-polarity voltage, for a gray scale, are applied alternately to each pixel. Polarity inversion, however, necessitates different common voltages for the respective liquid crystal panels, due to various reasons, such as parasitic capacitance generated during fabrication of a thin film transistor, characteristics of the thin film transistor, voltage uniformity in common voltage generating electrodes, or a structural difference between each of the circuit components.
A flicker phenomenon occurs due to a data voltage distortion, that is, the positive-polarity data voltage and the negative-polarity data voltage being asymmetric with respect to the common voltage. To minimize the occurrence of the flicker phenomenon a common voltage generation circuit may employ a digital variable resistor to enable an inspector to adjust a flickering level directly at an inspection stage. The time for adjusting the flickering level may vary depending on the inspector's skill. In addition, since the flickering level is observed with the naked eyes, quantitative control of the flickering level is less than satisfactory. Further, measurement errors may be introduced due to an inspector's physical fatigue or other ambient conditions.